Ophthalmic glass



Reissuecl Nov. 23, 1948 Re,

UNITED STATES" PATENT QFFICE.

OPHTHALMIC GLASS William H. Armistead, Corning, N. Y., assignor to CorningGlass Works, Corning; N. Y., a corporation oiv New York No Drawing. Original No. 2,433,883, dated January 6, 1948, Serial No. 691,663, August 19, 1946. Application for reissue February 11, 1948, Serial No. 7,731

16 Claims. (Cl. 10654).

This invention relates to transparent ophthal- It is particularly valuable for further increasing.

mic glasses, small buttons of which. are tobe the refractive indeX'wi-thout causing devitrificasealed-into lenses of crown glass for theproduction inglasses a i arye BaO contents, buttion of multifocal spectacle lenses. Glasses which it may also be added to the glass irrespective of are tobe used for this purpose must meet certain 5 the presence or absence of BaO. Up to 15% Cal) requirements. Above all, they must seal propmay thus be employed.

erly with, standard white optical crown glass Up to 8% A1203 maybe added, preferably but which has a thermal expansion coefficient of not necessarily in lieu of S102. Such addition. 93x10 cm. per cm. per degree C. and a softenincreases the resistance of the glass to devitriing point of about 725 C. Softening point is 10 fication.

that temperature at which a fibre of the glass 2 ay be n o ted in t elass ith ad of specified size will be elongate under its own Vantage to the optical properties and chemical...

weight at a given rate when suspended through durability. Both TiOz and ZIOz tendto raise the a small furnace of specified dimensions (Viscosity refractive index of the glass more than the other of GlassBetween the Strain Point and Melting oonstituentsbut, whereas ZrO2 has only a slight Temperature, by H. R. Lillie, Jo-ur. Am. Cer. Soc., effect on the dispersi e n e 2 a a St o vol. 14, page 502, July 1931 They must have depressing eiiect on it. Hence, I prefer to use good devitrification resistance during sealing and s uch Z Oz, between 4% and 15%, as will disadequate chemical durability or resistance to solve in the glass and to add as much TiOz as weathering. Their purpose requires an index'oi p bl Without unduly lowering t dispersive refraction for the D line (nD) between 1.57 and ind x p to z ay u be added.

1.70 and it is desirable that they have a dispersive h e pans n c fi t r su a e s a in t index (11) which is as high as possible; Prion the Standard Optical Crown glass Wil1 y eophthalmic glasses of high. refractive index have what with f nin -p nt n W h mp siti n.

a maximum dispersive index of about. 32 which and the nevi/classes will Se satisfactorily if.

is lessthan desired. The prior glasses of lower their expansion coefiicients are between 83 10-" refractive index have a maximum dispersive inand 95 10 om. pe cm. Der degree (1'. dex of about 50 but have insufficient chemical The following composi o s n w ht pe durability. centage as calculated from theirbatchesare The primary object of this invention is to given by way of example but not as limitations provide ophthalmic glasses which have higher of th n nt i dispersive indices than has hitherto been obtainablein glasses of this type without sacrifice of other desirable properties. 1 2 3 4 I 5 I 6 Another object is to provide ophthalmicglasses having optical properties ranging from nD.-=1.70, g f 2 preferably nD:1.65; 2 46, to nDzLS'l, pref" ZI'O2 10.2 10 s 7 5.5 erably nD:1.59. 11:53, but having at the. same 2T8; %3 time good chemical durability, softening pointsv L110- 3 2 2 2 2 below 700 C. and thermal expansion coefficients 40 E5; g between 83 and 95X 1(l' cm. per cm. per, degree C. pool... 1n 5 5 10 In general I have found that the above objects iggg 5 (if 5 "1 1 2 it may be attained with glasses comprising 33% to Ego -X 1 3 1 1 1 39 60% $102 1% to 7% B203 4% to 15% Z10? :...QIII:T: .Q "533 532 l l. his a the '4 s;

0% to 25% BaO, 3% to 15% Z110, .5% to 5% LizO, and 1% to 15% NazO. In view of NazQ', K20 may be substituted wholly or in part. Al- Compositions 5 and Bare particularly suitable though BaO'may be absent, the glass preferably for. combination with standard. optical crown should contain at least 5% thereof because BaO glass to produce bifocal lenses.

raises the refractive index without unduly lower- It, is characteristic of the new glasses that they ing the dispersive index. More than 25% BaO contain a substantial amount of ZrOs. Commay cause devitrification. Other oxides, if demercial zrot sometimes contains a small amount sired, may be added with benefit as follows: of uranium as an impurity which is sufilcient to CaO raises the refractive index, although on cause fluorescence in bright light. This somea percentage basis it is not as effective as BaO. times creates the appearance of an objectionable fog or haziness before the eyes when spectacle lenses composed of such glasses are worn in strong light. I have found that the objectionable fluorescence can be prevented by melting the glass under reducing conditions or by the addition of a small amount of Sn02. The latter decomposes sufliciently during melting to cause reduction of the uranium to a lower valence which does not fluoresce.

I claim:

1. An ophthalmic glass analytically containing 33% to 60% Si02, 1% to 7% B203, 4% to 15% H02, to 25% BaO, .5% to U20, 1% to 15% 171220 and 3% to 15% of an oxide of a metal of the second periodic group having an atomic Weight between 40 and 66, the softening point of the glass being below 700 C., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefficient being between 83 and and 95X 10- cm. per cm. per degree C. between 0 and 300 C.

2. An ophthalmic glass which comprises 33% to 60% Si02, 1% to 7% 13202, 4% to H02, 0% to 25% BaO, 3% to 15% ZnO, .5% to 5% U20, 1% to 15% 17220, the softening point being below 700 0., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coeiiicient being 83x 10"' and 95 10- cm. per cm. per degree C. between 0 and 300 C.

3. An ophthalmic glass which comprises 33% to 60% S102, 1% to 7% B202, 4% to 15% ZrOz, 0% to 25% Ba0, 3 %t015% ZnO, .5% to 5% L120, 1% to 15% Na20, up to 8% A1202, the softening point being below 700 C., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefficient being between 83 10" and 95 10- cm. per cm. degree C. between 0 and 300 C.

4. An ophthalmic glass which comprises 33% to 60% Si02, 1% to 7% B202, 4% to 15% R02, 0% to 25% B210, 3%to 15%Zn0, .5% to 5% H20, 1% to 15% Na20, up to 15% C20, the softening point being below 700 0., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefficient being between 83 10 and 95 10- cm. per cm. per degree C. between 0 and 300 C.

5. An ophthalmic glass which comprises 33% to 60% Si02, 1% to 7% B203, 4% to 15% 2102, 0% to 25% B20, 3% to 15% ZnO, .5% to 5% H20, 1% to 15% Na20, up to 10% Ti02, the softenin point being below 700 C., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefficient being between 83 10- and 95X 10" cm. per cm. per degree C. between 0 and 300 C.

6. An ophthalmic glass which comprises 33% to 60% Si02, 1% to 7% B202, 4% to 15% Zr02, 0% to 25% BaO, 3% to 15% ZnO, .5% to 5% L120, 1% to 15% No.20, up to 15% CaO and up to 10% Ti02, the softening point being below 700 0., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefiicient being between 83 10- nd 95x10 cm. per cm. per degree 0. between 0 and 300 C.

7. An ophthalmic glass which comprises 33% to 60% Si02, 1% to 7% B203, 4% to 15% M02, 0% to 25% BaO, 3% to 15% ZnO, .5% to 5% L120, 1% to 15% Na20. up to 8% Al202, and up to 15% Ca0, the softening point being below 700 C., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefllcient being be- 4 tween 83 10-" and 10-' cm. per cm. per degree C. between 0 and 300 C.

8. An ophthalmic glass which comprises 33% to 60% Si02, 1% to 7% B202, 4% to 15% Zr02. 0% to 25% BaO, 3% to 15% Zno, .5% to 5% Li20, 1% to 15% No.20, up to 8% A1202, and up to 10% Ti02, the softening point being below 700 0., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefllcient being between 83 10- and 95x10" cm. per cm. per degree C. between 0 and 300 C.

9. An ophthalmic glass which comprises 33% to 60% S102, 1% to 7% B202, 4% to 15% H02, 0% to 25% Ba0, 3% to 15% ZnO, .5% to 5% H20, 1% to 15% NazO, up to 8% A1202, up to 15% C220 and up to 10% Ti02, the softening point being below 700 C., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coeificient being between 83 10" and 95 l0 cm. per cm. per degree 0. between 0 and 300 C.

10. An ophthalmic glass analytically containing 33% to 60% $102, 1% to 7% B203, 4% to 15% ZrO, .5% to 5% Li20, 1% to 15% N220, and approximately 20% BaO, 5% 08.0 and 7.5% ZnO, the softening point being below 700 C., the reiractive index (nD) being between 1.57 and 1.70 and the thermal expansion coeflicient being between 83 10- and 95x l0' cm. per cm. per degree C. between 0 and 300 C.

11. An ophthalmic glass analytically containing 33% to 60% Si02, 1% to 7% 13203, 4% to 15% ZrO2, .5% to 5% L120, 1% to 15% M120, and approximately 20% B80, 5% 09.0 and 7.5% ZnO, and up to 10% Ti02, the softening point being below 700 0., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefficient being between 83 10-' and 95 10' cm. per cm. per degree C. between 0 and 300 C.

12. An ophthalmic glass analytically containing 33% to 60% B102, 1% to 7% B203, 4% to 15% ZrOz, .5% to 5% H20, 1% to 15% Na2O, and approximately 20% B210, 5% Ca0 and 7.5% XnO and up to 8% A1202, the softening point being below 700 0., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion coefiicient being between 83x10- and 95x10" cm. per cm. per degree C. between 0 and 300 C.

13. An ophthalmic glass analytically containing 33% to 60% Si02, 1% to 7% B202,=1% to 15% Zr02, .5% to 5% L120, 1% to 15% Na20, and approximately 20% BaO, 5% 03.0 and 7.5% ZnO, up to 10% T102, and up to 7% A1203, the softening point being below 700 C., the refractive index (nD) being between 1.57 and 1.70 and the thermal expansion cceflicient being between 83 10' and 95X 10- cm. per cm. per degree C. between 0 and 300 C.

14. An ophthalmic glass which consists approximately of 37.5% Si02, 4% 13202, 5.5% Zr02. 20% BaO, 10% ZnO, 2% H20, 4.5% Na20, 2% A1203, 10% C210 and 4.5% T102.

15. An ophthalmic glass which consists approximately of 44.5% Si02, 4% B202, 7% Zr02, 20% B30, 7.5% ZnO, 2% H20, 6% Na2O, 2% A1203, 5% 02.0 and 2% T102.

16. An ophthalmic glass which in parts by weight consists approximately of 44.5 Si02, 4 B203, 7 ZIOz, 20 138.0, 7.5 ZnO, 2 L120, 6 Na20, 5 C220 and 2 T102.

WILLIAM H. ARMISTEAD.

No references cited.

Certificate of Correction Reissue No. 23,049. November 23, 1948.

WILLIAM H. ARMISTEAD It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 12, strike out the word he; line 46, for view" reed lieu; column 4, line 23, claim 10, for ZrO" read ZrO line 42, claim 12, for XnO read ZnO; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uom/missimr of Patents. 

